Evaluation of SmITS1-LAMP performance to diagnosis schistosomiasis in human stool samples from an endemic area in Brazil

Abstract

Schistosomiasis is a life-threatening infectious disease categorized by the World Health Organization as a public health issue. New molecular diagnostic alternatives for intestinal schistosomiasis caused by Schistosoma mansoni, such as the loop-mediated isothermal amplification (LAMP), a fast and simple amplification technique, have been proposed for control of this NTD in low-endemicity locations. A LAMP assay was performed to detect the internal transcribed spacer 1 ribosomal gene of S. mansoni (SmITS1-LAMP) in 322 DNA extracted from stool samples from schistosomiasis endemic area in Brazil. Kato-Katz analysis of human stool samples was used as the gold standard test, detecting 144 positive samples. SmITS1-LAMP detection limit achieved a maximum analytical sensitivity of 10 fg/μL using S. mansoni genomic DNA, subsequently detecting 17/144 (11.8%) positive samples. SmITS1-LAMP sensitivity and specificity were 12% (95%CI: 7%–18%) and 93% (95%CI: 89%–96%), respectively. Positive predictive value (PPV) and negative predictive value (NPV) were 59% (95%CI: 39% - 76%); and 57% (95%CI: 51% - 62%), respectively. Most cases involved men (61.8%), predominantly young adults (20–39 years old) in cases diagnosed by Kato-Katz and adults (40–59 years old) in cases diagnosed by LAMP. The low number of eggs per gram of stool (1–99 EPG) was the most frequently identified by both Kato-Katz and LAMP. Further studies are needed to evaluate the applicability of SmMIT-LAMP on Schistosoma mansoni diagnosis and surveillance of schistosome infections.